Organization and parent-of-origin-specific methylation of imprinted Peg3 gene on mouse proximal chromosome 7

Peg3 is the first imprinted gene to be identified on mouse proximal chromos ome 7; the human PEG3 homologue is on chromosome 19q13.4. Peg3 encodes a C2 H2-type zinc finger protein that is expressed only from the paternal allele in embryos and adult brain. The gene has been shown to regulate maternal b ehavior and offspring growth and has been implicated in the TNF-NF kappa B signal pathway. Here we show that Peg3 consists of nine exons spanning 26 k b. The 5' region of the gene contains a region rich in repeated sequences a nd a CpG island. Analysis of expressed sequence tags revealed a transcript present upstream of the island and on the strand opposite to Peg3. These st ructural features and DNA sequences are conserved in mouse and human. The 5 ' region of Peg3 is preferentially methylated on the inactive maternal alle le, as shown by comparing embryos with paternal (PatDp, prox7) and maternal (MatDp.prox7) duplication of proximal chromosome 7. Recently, a new matern ally expressed Zim1 gene located downstream of Peg3 was identified, which s uggested that another imprinted cluster is present on proximal chromosome 7 . (C) 2000 Academic Press.